DE4217999A1 - High frequency surgery apparatus for cutting tissue - increases HF current until product of actual values of HF output voltage and current corresponds to adjusted power value - Google Patents

Abstract

The high frequency surgery appts includes a voltage sensor (9) to monitor the actual value of the HF output voltage UHF (Uist). The actual value (Uist) is compared with the desired value (Usoll). A device (11) calculates, for a deviation of the actual value, (Uist) from the desired value (Usoll), a maximum value (Imax) for the UF current (IHF) at an adjusted maximum HF-power (Pmax) and actual value (Uist). The calculating device generates an electrical signal (K) to an electronic power supply (7) to supply a current (IHF) to the output of the HF generator. The UF current is increased until the product of the actual HF output voltage (Uist) and actual value of HF current (Iist) corresponds to the adjusted power (Pmax). For actual HF output voltage (Uist) to equal desired value (Usoll) is dependent only in the resistance between the active and neutral electrode. ADVANTAGE - Generates short duration and also higher HF current or HF power if necessary.

Description

The invention relates to a high-frequency surgical device according to the preamble of Claim 1.

High-frequency surgical devices consist of at least one high-frequency generator and a power supply unit and facilities to limit and / or regulate the RF output power, the RF output voltage, the RF output current or the intensity of the electrical Arc between active electrode and tissue, devices for activating the High frequency generators and other common elements. With respect to that Patient safety, especially with regard to unintended thermal ge Web damage due to excessive HF currents or HF power may High-frequency surgical devices according to DIN / VDE 0750 part 202 or IEC 601 part 2-2 Deliver more than 400 watts of power averaged over a second. With regard to patient safety, especially with regard to accidental thermal tissue Damage to the surgeon as a result of excessive HF currents or HF powers recommended to adjust the intensity of the HF current or the HF power at the radio frequency Adjust the surgical device as low as possible for the intended incision and / or coagulation is just required. Setting or limiting the RF Electricity or RF power is problematic in that for a defined one RF currents or RF power required during a cut quality Vary the cutting process and from cut to cut more or less (see G. Farin, possibilities and problems of the standardization of Hochfre quenzleistung, in high frequency diathermy in endoscopy, Herg. G. Lex and K. Semm, Springer-Verlag Berlin Heidelberg New York). As a rule, the RF output line High-frequency surgical equipment set so high that the cutting electrode cuts quickly through the fabric from the beginning to the end of the cut, d. H. the HF Power is at least as high as the maximum during a cutting process performance stopped. To remove a polyp using a polypecto miesling, which is usually around the before activating the high frequency generator Placing polyps around is essential at the beginning of a cutting process higher RF power or a much higher RF current than during the actual cutting process.  

A high-frequency surgical cutting device is known from DE-A 34 20 340 C2, which has a high-frequency oscillator whose output signal via a control stage and a driver is applied to a high frequency generator, with the oscillator a switching arrangement actuated by the operator can be switched on and off. This Hochfre quenz surgical cutting device is characterized in that the control level by a controlled switch is bridged, the control input is connected to a timer switch stage is closed, the controlled switch immediately after actuation of the switching arrangement to increase the output power only for one to form a gas discharge between the contact with the tissue when the switching arrangement is actuated Cutting electrode and the tissue closes sufficient time.

Such a high-frequency surgical cutting device is pro in use blematic, than that for the formation of a gas discharge or ignition of electrical light arc between cutting electrode and tissue required time of different Boundary conditions, such as the effective contact area and the electrical Voltage between the cutting electrode and tissue is dependent. This time period becomes too set briefly, so the electric arcs stay off. If the time is too long set, there are violent electric arcs between the cutting electrode and Fabrics which thermally damage the fabric more than intended and / or even the Can damage the cutting electrode.

Another problem with the use of a high-frequency surgical device corresponds to chend DE-A 34 20 340 C2 is that the electric arc between The cutting edge electrode and tissue can go out during a cut if For example, a low-resistance tissue area has to be cut through briefly, the HF voltage if the power or current is set too low below the Ignition electric arc required level breaks down and a continuation It is therefore not possible to cut the cut, because at this point there is a similar approach cutting problem can arise; like at the beginning of the cut. To continue the cut must the surgeon reactivate the high frequency generator by a new one Generate power pulse.

It is an object of the invention to provide high-frequency surgical devices with relatively low HF Nominal currents or relatively low HF nominal power and / or with facilities for loading limit the HF current or the HF power so that if necessary, briefly even higher RF currents or RF powers are generated without the above  Disadvantages of the known high-frequency surgical device according to DE-A 34 20 340 C2 are present.

A high-frequency surgical device according to the invention is essentially with a high frequency generator, an electronically controlled power supply, a device for acti four of the high frequency generator, a device for automatic monitoring the RF output voltage and / or a device for monitoring the intensity of the electric arc between active electrode and tissue, a device for Limitation of the maximum HF power or the maximum HF current as well as with a Device for setting, controlling and / or regulating the HF output voltage or a device for setting, controlling and / or regulating the intensity of the electric arc between active electrode and tissue and with an elec tronic computer and suitable software.

The invention is based on the finding that for cutting biological tissue by means of HF current between the electrode used for cutting and the cutting biological tissue electric arcs must be present. The Invention is also based on the knowledge that for igniting electric light bo between a metallic electrode and water-containing biological tissue RF voltage with a peak of at least 200 volts is required. The Erfin Therefore, the assumption is made that a cut is possible if the spit Zen value of the HF voltage between the metallic elec trode and the water-containing biological tissue to be cut at least 200 volts or electric arcs are present. Therefore, the surgeon has to Cut either the RF output voltage of the RF generator to at least 200 Set a peak voltage or a minimum intensity of the electric arc.

However, cutting is only possible if the HF voltage between the Cutting used electrode and the tissue to be cut are actually sufficient is high that electrical arcs can ignite. Is it needed for cutting? The HF current is greater than the HF current that the HF generator as a result of current or Can deliver maximum power limitation, so the RF voltage breaks down to the Igniting electric arcs together is a necessary value and is a tissue cut not possible. In a high-frequency surgical device according to the invention is always then and only if the high-frequency generator is active for the purpose of cutting fourth or is and the RF voltage among those used to ignite electric arcs required value breaks down, the current limitation and / or the power limits software set by the electronic computer to a higher value, depending but only until the HF voltage required to ignite electrical arcs or an electric arc is present, taking into account the safety of the patient  ducks, however, so long that the product of active power and time or that in the Tissue introduced electrical energy does not exceed an adjustable maximum value. For example, the maximum value of the energy in the safety regulation for High-frequency surgical device IEC 601 part 2-2 specified power of 400 watts averaged over a second or 400 Ws. The RF voltage increases during this Time interval with increased maximum value of the HF current or the HF power does not occur the electronic arc sets the value required to ignite electric arcs Calculate the HF current limitation back to the previous, smaller one using software Maximum value back, with the result that the RF voltage may be very low collapses. In one embodiment of the invention, the electronic computer sets the HF current limitation does not return to a preset, fixed value, but calc net at short intervals the value of the RF current limitation as a quotient from the am High frequency surgical device set power limit and the respective mo mental RF voltage at the output of the high-frequency surgical device or the RF Voltage between active electrode and tissue.

As soon as the RF voltage reaches the level required to ignite electric arcs Value increases or electric arcs between the cutting electrode and tissue are present, the level of the RF output voltage or the intensity of the electri arc is automatically regulated to a previously set value.

The HF voltage collapses again below the value during a cutting process men, which is required to ignite electric arcs, the above be Written operation of an embodiment of the invention can be repeated automatically where at pause intervals can be inserted around the RF power, averaged over at for example 5 seconds, to a value that is harmless to the patient.

The properties of a high-frequency surgery according to the invention described above device can be used not only when cutting but also when coagulating the. This applies e.g. B. for the so-called. Forced coagulation, which is un cutting decides that the RF voltage is modulated in amplitude such that the cutting edge effect is suppressed.

With soft coagulation, with the electric arc between the coagulation electrodes trode and the tissue to be coagulated should be avoided and the peak value the HF voltage should therefore remain below 200 volts, only a smaller one RF voltage as 200 volts as a criterion for the above-described limit Er increases in the HF current limitation or HF power limitation.

The invention is described below using an exemplary embodiment and a schematic described in more detail.

As soon as the high-frequency oscillator 2 is activated by a start / stop device 1 , it delivers an RF control signal hf to the RF generator 3 , which generates the RF voltage U _HF at the output sockets 5 , 6 of the high-frequency surgical device Peak value is largely proportional to the operating voltage U _{B of} the electronic switching power supply 7 . The setpoint U _should the HF voltage U _HF can be set on a setpoint generator 8 . The HF voltage U _HF is automatically regulated to the target value U _soll by the actual value U _ist the HF voltage U _HF by means of an HF voltage sensor 9 in an electrical signal u proportional to the actual value U _ist the HF voltage U _HF is converted, which is fed to an analog-to-digital converter (ADC) 10 , from where it is fed to the electronic computer 11 , hereinafter referred to as CPU for short, where it is compared with the setpoint U _{soll of} the setpoint generator 8 . Deviates U _is U _soll from, the CPU 11 outputs a correction signal k, which the electronic switching power supply 7 is supplied via a digital-to-analog converter 12, and so controls that U _HF = U is _intended.

If the active electrode AE touches the biological tissue 13 , an HF current I _{HF flows} , which is dependent on the level of the HF voltage U _HF and the electrical resistance between the active electrode AE and the neutral electrode NE. With regard to the safety of the patient, the level of the HF current I _HF at a current limitation 14 can be limited to a non-hazardous value I _max . The actual value I _{HF of} the HF current I _HF is converted by means of an HF current sensor 15 into an electrical signal i which is proportional to this HF current and which is fed to the CPU 11 via an analog-digital converter 16 . If or is the electrical resistance between active electrode AE and neutral electrode NE so small that I _HF at U _HF = U Soll would _be greater than I _max or is or I _HF = I _max , the electronic computer 11 calculates in short time intervals by means of a suitable software, which it takes from an EPROM 18, from a 17 adjustable maximum at a power limit RF power P _max1 a new maximum value I _max1 for the RF current I _HF, which is the ratio of the maximum RF power P _max1 and the actual value U _, the HF voltage U _{HF is} calculated. The HF current I _HF is therefore only limited to the maximum value I _max if the actual value U _{ist of} the HF voltage is not less than the setpoint U _{soll of} the HF voltage. As long as U _is smaller than U _should , this high-frequency surgical device behaves like a generator with constant output power.

In order to ensure that the electrical resistance between the active electrode and tissue increases as quickly as possible to a value at which the setpoint value of the HF voltage _arises , it is expedient in various cases to use a higher maximum current than it derives from the power P _max1 and calculated the actual value of the RF voltage as a quotient. In these cases, a higher maximum value P _max2 can be set, for example in the amount of 400 watts averaged over a time of one second in accordance with IEC 601 Part 2-2. In this case, a time limit is additionally provided, which can be calculated for example with the help of the CPU 11 and suitable software from the actual values of the RF voltage and the RF current and taking into account the time. In this way it can be achieved on the one hand that the electrical resistance between active electrode AE and neutral electrode NE is increased very quickly to the value at which the setpoint value of the HF voltage is set and on the other hand that too much electrical energy is prevented in the tissue is inserted. The latter is prevented by calculating the current limit from P _max1 over a second after introducing a maximum power of P _max2 or automatically _resetting to the value I _max set on the current limit 14 or to zero. In addition, the HF current is automatically limited again immediately to the value I _max set on the current limit 14 if U _is = U _should .

If a high-frequency surgical device according to the invention is used for applications in which electric arcs between active electrode AE and tissue 13 are required, for example for cutting or for forced coagulation, the RF voltage can also be used instead of the setpoint / actual value comparison described above The setpoint / actual value comparison of the intensity of the electric arcs between the active electrode and the tissue can be used. For this purpose, a setpoint generator 19 as well as an actual value sensor 21 and an analog / digital converter 20 are provided. A combination of these two comparisons or criteria can advantageously improve the redundancy of this device.

In an advantageous development of the invention, the software can be designed in such a way that, in the event of rapidly repeating voltage and / or arcing breakdowns below the respective target value, the tissue is applied to the tissue over a longer period of time, for example during an uninterrupted activation of the HF generator 2 , 3 delivered power does not exceed a maximum mean value, for example P _max1 .

Claims (2)

1. High-frequency surgical device for cutting biological tissue, equipped with a high-frequency power generator and a setting device on which the high-frequency output power can be set, as well as a device for activating the high-frequency power generator and a device which is activated after each activation of the high-frequency power generator Time-limited allows a higher RF output power than the high-frequency output power set on the setting device, characterized in that a voltage sensor device ( 9 ) for automatic monitoring of the actual value of the RF output voltage UHF and / or an arc sensor device ( 21 ) for monitoring the intensity of the electric arcs between the active electrode (AE) and the tissue ( 13 ), it is provided that the actual value of the RF output voltage and / or the intensity of the electric arcs with a target value U _should the RF voltage or the actual value of the intensity of the electric arc event the intensity of the electric arc is compared with a desired value, that an electronic computer (11) is provided, which _is at a deviation from U _to U or F _is F _to a maximum value I _max for the RF current I _HF from a set maximum RF power P _max1 and U _is calculated to generate an electrical signal (k) which is an electronic power supply unit (7) is fed to a such high RF current I _HF to deliver at the output of the RF generator that of the RF current is increased until the product of _U, and I _is the set power P corresponds _max1, and that _is with U = U _soll and / or F _is = F _should , I _{HF is} only dependent on the electrical resistance between active and neutral electrode. 2. High-frequency surgical device for cutting biological tissue, equipped with a high-frequency power generator and a setting device on which the high-frequency output power can be set, as well as a device for activating the high-frequency power generator and a device which is activated after each activation of the high-frequency power generator Time-limited allows a higher RF output power than the high-frequency output power set on the setting device, characterized in that a voltage sensor device ( 9 ) for automatic monitoring of the actual value of the RF output voltage UHP and / or an arc sensor device ( 21 ) for monitoring the intensity of the electric arcs between the active electrode (AE) and the tissue ( 13 ) it is provided that the actual value U _is the RF output voltage U _HF and / or the intensity of the electric arcs with a target _to U value of the RF Voltage or the actual value of the intensity of the electric arcs is compared with a target value F _{soll of} the intensity of the electric arcs, that an electronic computer ( 11 ) is provided which, in the event of a deviation from U _ist from U _soll or from F _is F _to a maximum value I _HF for the RF current I _HF from a set maximum RF power P _max2 and U _is calculated to generate an electrical signal (k) which is an electronic power supply unit (7) is fed to to provide such a high RF current I _HF at the output of the HF generator, that the product of _U, and I _is the set power P _max2, and in that _max2 time for safety P by the electronic computer (11) and appropriate software or by reducing P _max2 to a value P _max1 which is harmless to the patient in such a way that the energy supplied to the patient averaged over time is limited to one for the patient Patient safe value is limited.